AN ALTERNATIVE TO PRODUCE VALUE ADDED BIOBASED PRODUCTS FROM SUGARCANE BAGASSE

CLAUSER, NICOLÁS; SOLEDAD GUTIERREZ; MARÍA CRISTINA AREA; FERNANDO ESTEBAN FELISSIA; MARÍA EVANGELINA VALLEJOS

Concepción

Simposio; Biorefineries, Science, Technology and Innovation for the Bioeconomy; 2015

Small-sized biorefineries are not capital intensive and have lower transportation cost, lesser movements of liquid and solid streams, and lower heat transfer problems than high-sized ones [1]. Xylitol production consists of the following stages: autohydrolysis of the hemicellulose of bagasse, concentration of spent liquor, acid post-hydrolysis, removal of inhibitors by adsorption, fermentation of xylose to xylitol, and xylitol recovery by crystallization. A simplified kinetic model was developed for the extraction of xylose in the autohydrolysis process. Kinetic constants kh and k1 were determined, and activation energies Ea and Ln(ko) for the kinetic reactions were calculated from the Arrhenius equations. Experimental data obtained by Vallejos et al., [2] were used for the autohydrolysis pretreatment step. Temperature and time for the maximum extraction of xylans with minimal energy demand were determined with the model. The conditions and reactions for the other stages of the process were selected from updated bibliography. In addition, costs and benefits that could be obtained by exploiting the residual solid feedstock were estimated. Sugarcane is so far the most efficient raw material for bioethanol production, involving four major unit operations: enzymatic hydrolysis, fermentation of sugars into ethanol, and ethanol recovery [3]. Pellets production could be an interesting alternative for the hydrolysis residue [4]. In this work, the economics of xylitol production from hemicelluloses versus other alternatives was evaluated. Two alternatives for the use of the solid fraction were proposed: (1) ethanol production or (2) pellets production. Figure 1 shows a simplified block flow diagram of the process to convert lignocellulosic materials into xylitol. Autohydrolysis treatment and evaporations are energy intensive operations because of high temperatures and large amounts of water involved. The most expensive equipments for the process would be the fermenter and the crystallizer (approximately 19% of total capital investment). In this scenario, 93.9 kg of xylitol could be obtained per ton of dry bagasse. The economic evaluation showed long recovery periods. However, optimization of different steps, as liquid to solid ratio of pretreatment, evaporation, or fermentation, could represent attractive and innovative alternatives to reduce the recovery periods of capital costs.